The present invention relates generally to a machine for manufacturing electrical conductors and more specifically, to an apparatus for forming twisted and offset bus conductors.
Motor control centers perform various protection and control functions in industrial settings. In such motor control centers, three-phase electric power is fed from main conductors in electric power distribution mains (mains) to the motor control center. Within the motor control center housing, internal electric power is fed from the main to the motor control center electrical components through horizontal and vertical bus conductors (bus bars). Electrical power is fed through the bus conductors to internal electrical components mounted within the drawers or buckets. The buckets contain electrical components such as one or more circuit breakers, starters, overload protectors, or pilot devices.
Vertical bus conductors are arranged within the motor control center to connect the horizontal bus conductors, which are positioned in the upper section, with the buckets, which are positioned in the lower section. Conventionally, spacers are used between vertical bus conductors and horizontal bus conductors to provide protection against short circuits which may occur when there is inadequate space between the case (ie. ground), and the bus conductors or between phases. To avoid the use of spacers and promote better electrical contact with the horizontal bus conductors which are mounted planar to a back wall of the motor control center, the vertical bus conductors are twisted such that a portion of the bus conductor forms a plane perpendicular to the back wall of the motor control center and a portion is parallel to the horizontal bus conductors. In this way, spacing between the vertical bus conductors is increased. In addition, the connection between the buckets and the bus conductors can be accomplished using clips which slidably accept the bus conductors. As a result of using such clips, the bus conductors can be slidably inserted into and removed from the motor control center. To implement the turn in the bus conductors, L-shaped brackets and similar bolted connections have been used. However, the use of brackets increases the number of bolted connections utilized. Increases in the number of bolted connections leads to higher parts cost and labor for construction and maintenance and higher electrical resistance at the bolted connections.
Typically, bus conductors have been manufactured with a twist using a conventional die and a press. However, when subjecting the twisted bus conductor to a second forming operation using a second die and second press, reproducibility is made difficult. Also, adding the second forming operation significantly increases the part production cost as well as the labor cost.
The above discussed and other drawbacks and deficiencies are overcome or alleviated by the present invention.
In an exemplary embodiment of the invention, a machine for shaping a bus bar comprises a first retaining device, a second retaining device, a twisting device and an offset mechanism. The first retaining device is arranged to secure a first section of the bus bar in a first plane. The second retaining device is arranged to secure a second section of the bus bar. The twisting device is connected to the second retaining device and rotates the second retaining device to twist the second section of the bus bar about a longitudinal axis of the bus bar positioning the bus bar in a second plane. The offset mechanism is connected to the first retaining device and is arranged to offset the second section of the bus bar in a third plane, the third plane generally parallel to the second plane.